Oscillation generator



June 2 1, 1938. E, UNDENBLAb 2,121,158

050 ILLAT ION GENERATOR Original Filed Feb. 21, 1955 INVENTOR. I NILS E. LINDENBLAD ATTORNEY.

Patented June 21, 1938 .UNITED STATES 2,121,158 OSOIILATION GENERATOR Nils E. Lindenblad, Port Jefferson, N. Y., minor to Radio Corporation of America, a corporation of Delaware ApplioationFebruary 21, 1935, Serial No. 7.413 Renewed March 8, 1937 24 Claims.

My present invention relates to short wave oscillation generation and deals particularly with a push-pull line controlled oscillator.

Transmission lines consisting of copper tubes one half wave length long at a desired operating frequency have been found admirably suited for frequency controlling push-pull oscillation generators. These lines are made linear, as described in my United States Patent N0.'2,095,990,

l0 granted October 19, 1937, or, to conserve space, have been made U-shaped, as described more fully in United States Patent No. 2,095,980, granted to C. W. Hansell, October 19, 1937. It is desirable, however, in order to conserve space, to use a shorter line such as a quarter wave length line for frequency controlling a push-pull oscillation generator. Such an arrangement, without approaching space limitation, could make use of a line of relatively larger diameter resulting in an improved power factor of operation which, for high frequency work, is very desirable.

Accordingly, a primary object of the present invention is to provide an arrangement wherein a quarter wave length resonant line may generally be used with various types of push-pull connected circuits, such as vacuum tubes, and more specifically for the frequency control of a push-pull oscillation generator Briefly, in carrying into effect this object, I provide apparatus for deriving from a quarter wave length line voltages of opposite phase which may be applied to controlling electrodes of a push-pull tube system. These out of phase voltages are derived from the line by means of coupling circuits which will be described more fully hereinafter.

In the accompanying drawing, which is purely illustrative and in no way limitative of my present invention, Figures 1 and 2 illustrate modifications wherein out of phase voltages are inductively obtained from a quarter wave length frequency controlling line for controlling a push-pull vacuum tube system, and Figures 3 and 4 are modiiications making use of serially connected reactances for obtaining out of phase controlling voltages.

Turning to Figure l, the frequency controlling line 2 consists of a metallic, preferably copper, tube one quarter wave length long and is housed within the metallic cylinder 4 grounded at 6. The concentric tubes 2, 4 form a resonant frequency controlling line and may be provided with means for preventing variations in tuning despite changes in ambient temperature, as described more fully in the copending application of F. H.

Kroger, Serial No. 1,489, filed January 12, 1935 and in F. H. Kroger United States Patent No. 2,077,800, granted April 20, 1037. In addition, the line system 2, 4 may be placed within a temperature controlled oven, not shown, for render- 5 ing the system still more immune from frequency variation due to temperature change. At a suitable coupling point P at a suitable loading distance from the grounded end G of the line 2, I place in inductive relation to the tube or line 2 the U-shaped loop 8 connected to the grids i0, i2 of vacuum tubes I4, iii. These tubes are also provided with anodes I8, 20 and filaments or cathodes 24, 22. The cathode circuit is shown diagrammatically and illustrates the cathodes as being connected together through a resistor 26 grounded at its midpoint by means of a grounding connection 28. The anodes I8, 20 are connected in phase opposition by means of a parallel tuned circuit 30 feeding into an output circuit 32. Modulating potential may be introduced in the plate lead 34 by means of modulation transformer 36.

' The loop 8 is supported by means of the insulator 38 and passes through the openings 40, 42 of the outer cylinder 4 of the frequency controlling line.

High, frequency current flowing longitudinally alongthe tube or line 2 produces a magnetic field which cuts the loop 8 in such a way as to produce opposite phase potentials on the grids l0, l2 of vacuum tubes i4, i6.

In the system shown in Figure 2 out of phase potentials are applied to the grids l0, l2 by means of the separate loops 40, 42 coupled to the lower portionP of the frequency controlling line 2. These loops may be tuned by means of the variable condensers 44, if desired. By considering the magnetic field about the line 2, it will be seen that flux building up and collapsing through the loops 40, 42 will cause the application of out of phase potentials to the grids I, I2 of the push-pull connected tubes i4, i8.

As shown in Figure 2, the cathodes 22, 24 are directly, grounded and energized by separate sources 50, 52. Grid bias is supplied by means of a grid biasing battery 54. The biasing potential from the source 54 is fed through the outer metallic cylinder 6 which is now above ground D. C. potential, but maintained at ground radio frequency potential by meansof bypassing condenser 56, and loops 40, 42 to the grids l0, l2. The anode circuit of the tubes i4, i6 of Figure 2 includes the inductive loop 58 which may be provided, if desired, with a parallel tuning condenser 80. As

before, modulating potentials may be fed through the plate potential lead 34 by means of a modulation transformer 30 which may introduce waves of audio frequency, super-audible frequency, or of a low radio frequency, as found desirable or useful.

A further modification for obtaining out of phase potentia for controlling a pair of tubes from a qua wave length line, which by the way may be ,i nade an odd multiple of a quarter wave length long when operating at some harmonically related frequency, is shown in Figure 3. conductively connected to the line 2 at point P are three serially connected reactances, the inductance coil I0, the condenser 12, and inductance coil 14. The far end of coil 14 is grounded as at I6. The circuit including the section of line G, P and the reactors 10, 12, I4 is series tuned at the operating frequency. The grids of the tubes ll, I6 are connected across the capacitive element I2 and hence receive out of phase controlling voltages.

In addition, as shown in Figure 3, output energy is taken inductively from the plate circuit 50 by means of the inductively associated loop 00. The filament circuit consists of a pair of conductors 02, supplied with heating potential by means of the source 00 at voltage nodal points as shown. This filament or cathode circuit may be tuned or adjusted in impedance by adjustment of length or by' adjustment of condenser 01 and/or condensers 00, 00. Moreover, the filament circuit of any of the modifications shown herein may take the form such as described in my copending applications Serial No. 603,310, filed April 5, 1932, Patent No. 2,052,576, granted Sept. 1, 1936, and Serial No. 651,809, filed January 14, 1933, Patent No. 2,052,888, granted September 1, 1936. Grid bias is provided by means of the leak resistors I00 and a bypassing condenser I02 may be connected in shunt with the filament heating source as well as across the filament ends of the filament conductors 02, 84 which act in parallel for high frequency currents, but in series for filament heating currents.

In the system shown in Figure 4, the line 2 is conductively connected at point P to the condenser I04. Condenser I0 is serially connected to ground 16 through the inductance coil I06 and condenser I00. The circuit including the section of line G, P, condenser I04, inductance I00, and condenser I08 is series resonant or adjusted to be series resonant at the desired operating frequency. Across the grid coil I06, through which is fed grid biasing potential by means of lead I I0, out of phase potentials at the operating frequency arise and these are fed, as shown, in phase opposition to the grids i0, I2. The anode circuit 30 may be of the type shown in Figure 1 and the cathode circuit may include the choke coils H2 and adjusted in impedance as described in connection with the cathode circuit of Figure 3 by means of condensers 00 and 80.

While my present invention has been described in connection with oscillation generators, it should be clearly understood that it is not limited thereto. For example, this method of connecting a quarter wave length line in phase opposition to a pair of terminals, represented by the grids in this case, maybe used in other instances as, for example, where such a quarter wave length line is to be connected to a pair of terminals acting in phase opposition in a filter circuit, or, for example, in a frequency selective amplifier circuit.

By the term "odd multiple" as used in the ap-- pended claims, it is to be distinctly understood, is meant any odd multiple including one. Similarly, the term "ground used in the specification and claims is intended to mean a surface or point of zero or relatively fixed radio frequency potential. Also the term one-quarter of a. wavelengt is intended to mean a length which is electrically of this length, although it will be appreciated that in many cases both the physical and electrical length may be the same.

Having thus described my invention, what I claim is:

1. In combination, a linear element substantially one quarter of a wave length long, a pair of vacuum tubes, and means coupling an electrode of one tube and a corresponding electrode of the other tube in phase opposition to one end 'of said element.

2'. In combination, a linear element substantially one-quarter of a wavelength long, a metallic tube surrounding said element, a connection from said metallic tube to ground, a pair of vacuum tubes, and means coupling an electrode of one tube and a corresponding electrode of the other tube in phase opposition to one end of said element.

3. In combination, a linear element substantially one-quarter of a wavelength long, a pair of vacuum tubes each having a grid, and means coupling said grids in phase opposition to one end of said element.

4. In combination, a linear element substantially one-quarter of a. wavelength long, a metallic tube surrounding said element, a connection from said metallic tube to ground, a pair of vacuum tubes each having a. grid, and means cou- 'pling said grids in phase opposition to one end of said element.

5. In oscillatory apparatus, a metallic tube substantially one quarter wave length long, means grounding one end of said tube, a cylinder about said tube and connected thereto, a pair of vacuum tubes each having a grid, and means inductively coupling said grids to a portion of said metallic tube near its grounded end whereby said metallic tube produces on said grids potentials of opposite phase.

6. In oscillatory apparatus, a metallic tube grounded at one end, a cylinder about and connected to said tube. a connection including a capacitance reactance, and an inductance reactance connected between a point on said metallic tube near its grounded end and ground, a. pair of vacuum tubes, and means connecting corresponding electrodes of said vacuum tubes across one of said reactances.

7. Apparatus in accordance with claim 6, characterized by the fact that said connection includes, in the order named, the series circuit of said inductance, said capacitance and another inductance, and being further characterized by the fact that grids of said tubes are connected across said condenser.

8. Apparatus in accordance with claim 6, characterized by the fact that said connection includes, in the order named, the series circuit of said capacitance, said inductance and another capacitance, and being further characterized by the fact that grids of said tubes are connected across said coil.

9. In combination, a. substantially straight, low loss, frequency determining element in the form of a single conductor, a pair of vacuum tubes, and means coupling an electrode of each of said tubes in phase opposition ,to substantially one end of said element.

10. In combination, a low loss frequency determining element having a relatively large current conducting surface, a pair of vacuum tubes, and means coupling an electrode of each of said tubes in phase opposition to substantially one end of said surface.

11. In combination, inner and outer concentric conductors conductively coupled together at one of their adjacent ends, said inner conductor having a length substantially equal to an odd multiple of one quarter the length of the fundamental wave, a pair of electron discharge devices each having an anode, a cathode and a control electrode, connections coupling corresponding electrodes of said devices together, said connection between said control electrodes being so constructed and arranged with respect to said inner conductor that potentials on said inner conductor are applied to the control electrode of one device out of phase with respect to the potentials applied to the control electrode of the other device.

12. In combination, an oscillatory circuit comprising inner and outer concentric conductors,

said inner conductor having a length substantially equal to one quarter of the length of the fundamental wave, a connection from groundnto both of said conductors, a pair of electron discharge devices each having an anode, cathode and control electrode, connections coupling corresponding electrodes of said devices together, said connection between said control electrodes including a reactance having one terminal conductively connected to said inner conductor and the other terminal conductively connected to ground.

13. A system in accordance with claim 12, characterized in this that the connection between said cathodes is a tuned circuit to whose nodal points are connected a source of heating energy.

14. In combination, an, oscillatory circuit comprising inner and outer concentric conductors, said inner conductor having a length substantially equal to one quarter of the length of the fundamental wave, a connection from ground to both of said conductors, a pair of electron discharge devices each having an anode, cathode and control electrode, connections coupling corresponding electrodes of said devices together, said connection between said control electrodes including a reactance having one terminal capaci tively coupled to said inner conductor and the other terminal capacitively coupled to ground.

15. An oscillation generator circuitcomprising in combination a frequency controlling element in the form of inner and outer concentric conductorsconductively coupled together at one of their adjacent ends, said inner conductor having a length substantially equal to one quarter of the length of the fundamental wave, a pair of electron discharge devices connected in push pull relation, each having a control electrode, a loop circuit coupling the control electrode of each tube with said inner conductor in such manner as to induce potentials on said electrodes which are out of phase with respect to each other, said loop circuits each having a straight linear portion located adjacent to and extending parallel to the length of said inner conductor, whereby the magnetic field around the inner co'nductor induces potentials in said loops.

16. A system in accordance with claim 15, in-

. said two portions of said circuit in phase opposition to said element near said one end.

18. In combination, a resonant concentric line having an effective length substantially onequarter of the operating wave, said line consisting of an inner conductor and an outer conductor directly connected together at one end, a circuit having two conductors adapted to have instantaneous currents of opposite polarity flowing therein, and means comprising a pair of loops coupled to said inner conductor in opposite senses near said one end thereof for coupling said two conductors in phase opposition to said line.

19. In combination, a tuned high frequency circuit comprising a pair of concentric conductors coupled together at one of their ends more closely than at their other ends, a circuit adapted to have instantaneous currents of opposite polarity in two portions thereof, and means coupling said two portions in phase opposition to said tuned circuit near said one end.

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20. In combination, a tuned high frequency phase opposition to said tuned high frequency circuit.

21. In combination, a tuned high frequency circuit comprising a pair of conductors concentri-' cally arranged for at least a portion of their lengths, said conductors being coupled together at one part more closely than at another part, a circuit adapted to have instantaneous currents of opposite polarity in two portions thereof, and means located between said pair of conductors coupling said two portions in phase opposition to said tuned high frequency circuit, said means comprising two loops of wire coupled in reverse phase to the inner conductor of said pair.

22. In combination, a tuned high frequency circuit comprising a pair of conductors concentrically arranged for at least a portion of their lengths, said conductors being coupled together at one part more closely than at another part, a circuit adapted to have instantaneous currents of opposite polarity in two portions thereof, and means located between said pair of conductors coupling said two portions in phase opposition to said tuned high frequency circuit, said means comprising a single loop of wire coupled to the inner conductor of said pair near said more closely coupled part of said tuned high frequency circuit.

23. In combination, a linear element substan tially one-quarter of a wavelength long, a metallic tube surrounding said element and coupled at one end to said element, a circuit adapted to have instantaneous currents of opposite polarity in two portions thereof, and means coupling said two 5 portions of said circuit in phase opposition to said element near said one end. a

24. In combination, a low loss frequency determining circuit comprising outer and inner relatively large current conducting surfaces, a pair of vacuum tubes, and means coupling an electrode of each of said tubes in phase opposition to substantially one end 0! said inner surface.

NILE E. IJNDENBLAD. 

